In a conventional elevator signal transmission system, each elevator stop, i.e., each floor, is equipped with one or more signal terminal means comprising control buttons and indicator lamps. A passenger pushes a control button to produce a hall call which identifies the floor at which the passenger wishes to enter an elevator car and the direction, up or down, the passengers wishes to go. A control unit registers the hall call and directs an elevator to proceed to the floor to pick up the passenger. An indicator lamp in the signal terminal means lights to indicate that the hall call has been registered. In systems where more than one signal terminal means is disposed on the floor, each corresponding indicator lamp in each signal terminal means lights to indicate that the hall call has been registered. At each floor, some of the control buttons and lamps are used for ascending purposes, while the remaining buttons and lamps are employed for descending purposes. The lowest floor has only lamps or buttons used for ascending purposes. Likewise, the uppermost floor has only lamps or buttons used for descending purposes.
Signals produced by the control buttons are typically processed with solenoid relays incorporated in the control unit, typically installed in a machine room on the roof of the building. One signal line and one relay are needed for each button. The control unit produces signals which drive the lamps. Each lamp requires one signal line. Therefore, if the building has n floors, as many as 4n-4 signal lines are required to connect the control unit in the machine room with the lamps and buttons installed in the various signal terminal means at the floors. For this reason, the conventional system requires a large number of long signal lines for tall buildings.
In an attempt to reduce the number of signal lines needed, an improved signal transmission apparatus for an elevator has been proposed in, for example, Japanese Patent Laid-Open No. 69685/1983. In the improved system, each signal terminal means receives or transmits a given type of information over the same line in a time-shared fashion and in synchronization with a reference signal which authorizes one signal terminal means at a time to use the line. This proposed apparatus is now described by referring to FIGS. 1-3. A control unit 1 for an elevator comprising a microcomputer is installed in a machine room. The control unit 1 acts to produce clock pulses and reference signals. Also, the unit 1 calls the elevator car and registers the floors from which the elevator car is called. Signal lines 2 are connected to the control unit 1. The signal lines 2 are disposed in an elevator shaft, running the length of the shaft. Clock pulses 3a which are produced at given intervals, e.g., of 500 microseconds, are transmitted through a clock line 3. A hall call signal line 4 is used to convey a hall call signal 4a produced at a stop. A register line 5 is employed to transmit a hall call register signal 5a.
In FIGS. 1-3, an elevator signal transmission system in a nine-story building is depicted. For illustrative purposes, one signal terminal means 101-109 with one control button and one indicator lamp is shown per floor. It will be understood, however, that on each floor, other than the uppermost and lowest floors, each signal terminal means will have two buttons and two lamps for ascending and descending.
Memories, herein shown as D-type flip-flops 81-89, are installed at ninth through first floors, respectively, and together make up a ring counter. This is a flip-flop corresponding to each signal terminal means for each direction of travel. Since each signal terminal means shown in FIG. 2 has one button and one lamp, there is one flip-flop corresponding to each signal terminal means. If a signal terminal means had two buttons and two lamps to support both ascending and descending, two flip-flops would correspond to the signal terminal means, one for each direction. Each signal terminal means is connected to receive reference signals from the flip-flop or flip-flops corresponding thereto.
To provide a clock signal to the flip-flops 81-89, the terminal CL of each flip-flop 81-89 is connected to the clock line 3. A reference line 91 connects the control unit 1 with a D input of the flip-flop 81. The control unit 1 transmits over the reference line 91 a reference signal 91a, illustrated in FIG. 3. The reference signal 91a, normally in a logical low state, makes a transition to a logical high state. The signal 91a remains in the high state for one cycle of the clock 3a plus a short additional delay and then returns to the logical low state. Reference lines 92-99, running between adjacent floors, connect respective Q outputs and D inputs of flip-flops 82-89 as shown in FIG. 2. As the flip-flops 81-89 receive successive clock pulses 3a, each of the flip-flops 81-89 making up the ring counter in turn outputs high reference signals 91a-99a, as shown in FIG. 3. Thus, each signal terminal means, in turn, receives a high logical state reference signal. To permit a given signal terminal means to use a line undisturbed by other signal terminal means, components of signal terminal means may be enabled by the reference signal. Components of the signal terminal means 101-109 which are enabled by the reference signals 91a-99a are said to operate in synchronization with the reference signals 91a-99a. Since only one signal terminal means at a time has a high reference signal, synchronization with the reference signal permits data transfers to or from a desired signal terminal means over the register line 5 and the hall call signal line 4 even though the lines 4, 5 are common to all signal terminal means.
To permit passengers to enter hall calls, control buttons 61-69 are provided in the signal terminal means 101-109. To sequentially enable hall calls onto the hall call signal line 4 in synchronization with the reference signals 91a-99a, logic devices, herein shown as AND gates 121-129, have first inputs connected to the reference lines 91-99, respectively, and second inputs connected to the control buttons 61-69, respectively. The outputs of the AND gates 121-129 are connected with the hall call signal line 4.
Indicator lamps 71-79 light to indicate registered hall calls. To hold registered hall calls and drive the lamps 71-79, Q outputs of D-type flip-flops 111-119 are connected to the lamps 71-79. To latch registered hall calls into the flip-flops 111-119 in synchronization with the reference signals 91a-99a, the terminals CL of the flip-flops 111-119 are coupled to the terminals Q of the flip-flops 81-89, respectively. The registered hall calls are provided from the control unit 1 as the hall call register signal 5a over the register line 5 to D inputs of the flip-flops 111-119.
If, for example, the button 62 at the second floor is pressed, the output of the AND gate 122 will rise in synchronization with next-occurring reference signal 92a. The output of the AND gate 122 is conveyed as the hall call signal 4a to the control unit 1 through the signal line 4. If the button 63 at the stop for the third floor is pressed, the output from the AND gate 123 rises in synchronization with the next-occurring reference signal 93a. The output of the AND gate 123 is transmitted as the hall call signal 4a over the same signal line 4. If the two buttons 62 and 63 are depressed simultaneously, the call signals 4a are conveyed in succession over the same call signal line 4, as illustrated in FIG. 3. These operations are repeated, in turn, to obtain the state dictated by one or more of the buttons 61-69. After a given number of clock pulses 3a are sent out, all the data is collected. These signals are processed by the control unit 1 and registered as hall call signals.
The hall call register signal 5a is transmitted from the control unit 1 through the registration line 5 to the input to the terminal D of the flip-flops 111-119. The hall call register signal 5a is synchronized with the reference signal 91a so that, when the reference signal for a given flip-flop 81-89 of the ring counter is clocked high, the registration line 5 will at that moment be carrying the hall call register signal for the respective signal terminal means 101-109. The output of the ring counter flip-flop 81-89 clocks the hall call register signal into the latch flip-flop 111-119. The high output of the latch flip-flop 111-119 then lights the lamp 71-79, indicating that the hall call has been registered.
In this conventional elevator signal transmission apparatus using time-shared signal lines, only the four signal lines 3-5 and 91 are needed to connect the signal terminal means 101-109 to the control unit 1. The number of signal lines is independent of the number of floors and the number of signal terminal means per floor, so this apparatus is especially suited for tall buildings with many floors.
A problem can arise if a signal terminal means outputs a hall call signal out of synchronization with the reference signal. If the circuit connected to the output of the AND gate 121 is short-circuited, for example, the hall call signal 4a is maintained high. A continuous high hall call signal 4a is interpreted by the control unit 1 as simultaneous, continuous hall calls from all floors. If such a problem occurs, the elevator car stops at every floor. Hence, service is undesirably slow. This type of problem is difficult to repair quickly because there is no easy way to tell which signal terminal means has the short-circuit. Each serial terminal means 101-109 must be checked separately for short-circuits until the defective serial terminal means is found.